School of Engineering

Fluoride removal from water using Al(OH)3-surface modified diatomite mixed with brick: optimization, isotherm and kinetic studies

Mon, 01 Jan 2024 00:00:00 GMT

Fluoride removal from water using Al(OH)3-surface modified diatomite mixed with brick: optimization, isotherm and kinetic studies Mutai, Isaiah Kiprono; Kiriamiti, Henry Kirimi; M’Arimi, Milton M; Tewo, Robert Kimuta Excess fluoride in drinking water causes both dental and skeletal fluorosis among other problems. As such there is need to develop affordable and easily accessible techniques for fluoride removal from drinking water. This work assessed surface modified diatomite mixed with brick for f luoride removal. Diatomite samples were modified using aluminium hydroxide and the mixture was optimized for fluoride removal through response surface methodology (RSM) using the Box-Wilson central composite design. Batch experiments showed that, individually, a 28 g/L dose of the surface modified diatomite sufficiently removed fluoride to the acceptable level of 1.5 mg/L from an initial concentration of 10 mg/L fluoride while a 300 g/L dose of brick powder was required to remove an equal amount of fluoride in the same water samples. RSM optimization showed that a mixture of surface modified diatomite and brick in the mass ratio 1.8:17.8 grams per milligram of fluoride in water can be used to remove fluoride in water to an acceptable level. Adsorption of fluoride by surface modified diatomite fit better into the Freundlich adsorption isotherm (R2=0.9753) compared to the Langmuir (R2=0.8954), while adsorption by brick better fit the Langmuir adsorption mechanism (R2=0.9804) in comparison to the Freundlich adsorption (R2 =0.9372). Kinetic studies revealed that chemisorption was the main mechanism for both surface modified diatomite and brick adsorbents. Conclusively, an optimal mixture of surface modified diatomite and brick can be successfully used fo

Functionalization of rice husk for high selective extraction of Germanium

Tue, 01 Apr 2025 00:00:00 GMT

Functionalization of rice husk for high selective extraction of Germanium Nzila, Charles; Qunshan, Wei t is of strategic significance to extract germanium (Ge) in an ecological way for sustainable development. Adsorbents that already adsorb Ge have disadvantages such as poor selectivity and low adsorption capacity. In this study, a novel adsorbent material based on rice husk functionalized with tannic acid was developed for the efficient extraction of Ge from simulated coal fly ash leachate. The adsorption capacity of tannic acid-functionalized rice husk (TA-EPI-ORH) for Ge was 19.9 times higher than that of untreated rice husk, demonstrating significantly improved performance. The results showed that the adsorption process of Ge by TA-EPI-ORH is consistent with pseudo-second-order kinetic and Freundlich isotherm model. TA-EPI-ORH had excellent selective adsorption properties, with adsorption of 1.40 mg L⁻¹ Ge exceeding 95% and solid-liquid partition coefficients of 4380 mL g⁻¹, even in the presence of nine impurity metal ions (average concentration: 479.08 mg L⁻¹). When compared with the two main coexistence ions—aluminum (Al) and calcium (Ca)—both of which have the relatively highest concentrations (Al: 1594.20 mg L⁻¹, Ca: 1740.13 mg L⁻¹), the separation factors for Ge still maintain relatively high level with SF(Ge/Al) = 42.57 and SF(Ge/Ca) = 39.93. Compared to existing studies, TA-EPI-ORH exhibits superior selective adsorption performance even with the presence of more interfering ions. After elution of the adsorbed Ge from TA-EPI-ORH, the extraction rate of Ge with low initial concentration (1.40 mg L⁻¹) reached 85.17%, while the extraction rates of Al and Ca were only 1.02% and 1.18%, respectively. Further research revealed that the catechol groups on the surface of TA-EPI-ORH formed stable complexes with Ge, whereas the complexes with coexisting ions (e.g., Ca and Al) were unstable, thereby ensuring high selectivity for Ge. This green chemistry-based functionalization of rice husk not only enables high-value utilization of agricultural waste but also provides a sustainable and eco-friendly strategy for efficient Ge separation and recoveryI

Barriers to the Growth and Implementation of Biogas Technology: The Kenyan Experience

Mon, 01 Jan 2024 00:00:00 GMT

Barriers to the Growth and Implementation of Biogas Technology: The Kenyan Experience Mutahi1, Purity M; Kimutai, Stephen K.; Adaramola, Muyiwa S Households in sub‐Saharan Africa predominantly rely on biomass energy for cooking, which has negative impacts on health and the environment. Biogas technology presents a promising alternative for developing nations like Kenya, yet its adoption faces multiple barriers at both individual and systemic levels. The study aims to investigate the obstacles to biogas development and adoption in Kenya. Thirty‐two (32) biogas experts from the renewable energy, biogas, and government & policy sectors were randomly selected for the study. Data were collected through structured questionnaires and analyzed using the Analytic Hierarchy Process (AHP), to prioritize the main barriers, with reliability ensured through a consistency ratio (CR < 0.1). Findings revealed high participant understanding and involvement, with economic factors being identified as the most significant barrier (weight = 0.4163). Other challenges included technical (0.3541), societal (0.0859), infrastructural (0.0734), and policy‐related issues (0.07040). Lack of awareness about biogas benefits emerged as the top sub‐criterion (0.4960), followed by poor distribution infrastructure (0.4286) and technician availability (0.4278). In conclusion, the study found that enhancing technical support, improving infrastructure, and raising awareness about the benefits of biogas are crucial for its wider adoption. The study recommends public awareness and educational training programs to improve overall understanding, capacity‐building initiatives to improve technical expertise, and further studies focusing on the exploration of affordable technologies, such as cost reduction methods, scalable production techniques, or localized innovations for rural areas.

Recent trends in the application of photocatalytic membranes in removal of emerging organic contaminants in wastewater

Wed, 01 Jan 2025 00:00:00 GMT

Recent trends in the application of photocatalytic membranes in removal of emerging organic contaminants in wastewater Nelson, Kipchumba; Mecha, Achisa C.; Samuel, Humphrey Mutuma; Suliman, Zeinab A. Increasing water pollution by bio-recalcitrant contaminants necessitates the use of robust treatment methods. Individual treatment methods are not effective against these emerging organic pollutants due to their stability in the environment. This has necessitated the use of advanced integrated systems such as photocatalytic membranes. Synergy in the reactive photocatalytic membranes effectively degrades the emerging organic pollutants. This review presents the state of the art in the synthesis and application of photocatalytic membranes in water and wastewater treatment. The study critically evaluates pertinent aspects required to improve the performance of photocatalytic membranes, such as tailored material synthesis, membrane fouling control, improved photocatalyst light absorption, use of visible light from sunlight, enhanced reaction kinetics through synergy, and regeneration and reuse. Previous studies report on the effectiveness of photocatalytic membranes in the removal of organic contaminants in synthetic and actual wastewater. As such, they show great potential in wastewater decontamination; however, they also face limitations that need to be addressed. The review identifies the challenges and provides a way forward in increasing the photoactivity of titanium oxide, fouling mitigation, scalability, improving cost effectiveness, enhancing membrane stability, and other aspects relevant in scaling up efforts from the lab scale to industrial scale.